Networking hardware, Switches and routers, have not traditionally been programmable entities. Instead, network hardware is configured using command line interfaces or external applications and a console connection. Some programming frameworks running on connected hosts or appliances are can also be used to manage network hardware. These approaches put applications managing the network on systems external to the network itself.
While most network management occurs via command line interfaces or configuration tools, some network devices may be configured to respond to specific events that occur on a given network device. For example, embedded event manager (EEM) is a feature included by Cisco's IOS operating system (and some other Cisco operating systems such as IOS-XR, IOS-XE, and NX-OS). EEM allows the behavior of a Cisco network device (e.g., a switch or router) to adapt to some user requirements by supporting a limited set of events and actions performed in response to such events within the network device itself. Using EEM, some problems can be identified and resolved automatically in advance by setting event triggers (called event detectors) to watch for specific types of situations or thresholds, or run a set of actions periodically.
At the same time EEM, and other network management frameworks, does not support the handling of custom or arbitrary events. That is, while EEM can be used to configure a switch or router to respond to a limited set of events, the range of such events is limited to whatever is pre-configured for a given switch. Thus, EEM does not allow network elements to respond to arbitrary user-specified events, custom protocols, or other compound or complex events. Further, the event processing provided by EEM (and other similar technologies) is limited to processing events local to the switch itself.